Display panel of a non-self-luminous display (such as, a liquid crystal display) cannot emit light; a backlight is thus needed to provide backlighting for the display panel. Currently, backlights can include Cold Cathode Fluorescent Lamps (CCFL), Hot Cathode Fluorescent Lamps (HCFL), Light Emitting Diodes (LED), and other electroluminescence (ELC) components. LEDs are prevalently used as backlights of liquid crystal display (LCD), for high color saturation, no mercury, long life, low energy consumption, and adjustable color temperature according to driving current.
Currently, in order to reduce power consumption of LED backlight of the LCD and/or enhance the display contrast, PWM dimming mode is proposed to use PWM signal to drive LEDs and thus dynamically adjust backlight brightness of LED backlight. However, the current LED driving mode has the following disadvantages: (a) driving current of the LED is a fixed value and cannot be automatically adjusted according to usage of the LED; (b) the driving current of the LED is fixed to the current at the maximum gray-scale brightness, while driven at non-maximum gray-scale brightness by use of the fixed current 1, the LED will work in a low efficiency area.